Standards for the design of signal word panels specify different combinations of colors, signal words, and a hazard alert symbol. The warning sign standards of the American National Standards Institute specify a yellow signal word panel, with the word Caution and a hazard alert symbol, for signs marking people hazards. The same panel, without the symbol, is intended for property hazards. The purpose of this study was to determine if the presence or absence of the symbol effectively conveys the intended severity messages. A sample of 59 college students rated their impressions of a Caution sign with and without the symbol. Subjects rated the plain Caution sign as communicating significantly higher severity levels than property damage, indicating that a yellow Caution sign inaccurately communicates a hazard to property. Subjects rated the sign with the symbol as connoting significantly greater severity than the sign without the symbol.
Jensen, R.C. and McCammack, A.M. (2003). Severity message from hazard alert symbol on caution signs. Proceedings of the Human Factors and Ergonomics Society, 47, 1767-1771.